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Starting Wednesday, owners of these Apple devices can download a free application, Kindle for iPhone and iPod Touch, from Apple’s App Store. The software will give them full access to the 240,000 e-books for sale on Amazon.com, which include a majority of best sellers.

The move comes a week after Amazon started shipping the updated version of its Kindle reading device. It signals that the company may be more interested in becoming the pre-eminent retailer of e-books than in being the top manufacturer of reading devices.

But Amazon said that it sees its Kindle reader and devices like the iPhone as complementary, and that people will use their mobile phones to read books only for short periods, such as while waiting in grocery store lines.

“We think the iPhone can be a great companion device for customers who are caught without their Kindle,” said Ian Freed, Amazon’s vice president in charge of the Kindle.

Mr. Freed said people would still turn to stand-alone reading devices like the $359 Kindle when they want to read digital books for hours at a time. He also said that the experience of using the new iPhone application might persuade people to buy a Kindle, which has much longer battery life than the iPhone and a screen better suited for reading.

Amazon also said its recently unveiled Whispersync function would work for people who own a Kindle and one of the Apple devices. They can access their library of previously purchased e-books on all of their devices at no additional cost. Amazon will also create automatic bookmarks, so that a user can stop reading a book on one device and pick it up on another device at the same spot in the text.

The move by Amazon tangles competitive dynamics in the growing e-book industry. Many analysts thought pocket-size versatile smartphones could eventually eat into the small but growing market for stand-alone book readers that do little else and still do not have color screens or full-featured Web browsers. With the announcement, Amazon appears to be hedging its bets.

Analysts had also thought Amazon was closely following the template Apple had created with the iPod and trying to dominate the market with a ubiquitous, must-have consumer electronics device. Now it appears Amazon is more interested in selling as many e-books as possible on its site, and collecting the royalties, while strengthening its ties with customers, many of whom will buy other products from Amazon if they start buying e-books.

“A couple months ago a lot of people thought Amazon was slavishly imitating the Apple model,” said Bill Rosenblatt, president of the consulting business GiantSteps Media Technology Strategies. “It turns out they have a different model than Apple. They are smarter than everyone thought.”

The developments also suggest that, true to his word, Steven P. Jobs, Apple’s chief executive, has little interest in the market for digital books. Mr. Jobs once dismissed the Kindle by saying “the whole conception is flawed at the top because people don’t read anymore.”

Unlike other forms of media like music and video, which Apple sells itself to iPhone owners through its iTunes store, Apple appears to be ceding the e-books market to Amazon and other companies that offer e-book applications.

“Apple is consciously skipping the e-book market,” said Evan R. Schnittman, vice president for business development and rights at Oxford University Press. “I think it’s pretty significant.”